Longitudinal pumping of Nd:YAG by laser diodes is well established, producing excellent performance in terms of power and efficiency, see the article by R. Scheps, entitled "Efficient Laser Diode Pumped Nd Lasers," Appl. Opt. 28, pp. 89-91, January 1989. Alexandrite, which is chromium-doped chrysoberyl (Cr:BeAl.sub.2 O.sub.4) is a tunable visible laser that operates between 700 and 820 nm and would be ideally suited for a number of applications if acceptable efficiency could be demonstrated, note the article by J. C. Walling et al. entitled "Tunable Alexandrite Lasers," IEEE J. Ouant. Electron. OE-16, pp. 1302-1315, December 1980. With the recent introduction of commercial 5 mW laser diodes operating in the 670-680 nm range, diode pumping of alexandrite is now possible but requires combining the output of several such devices. Higher power visible diodes are reported by O. Kumagai et al. in their article, "680 nm AlGaInP Visible Lasers Grown by MOCVD," Proceedings of the SPIE, L. E. Cramer et al. editors, Vol. 898, pp. 80-83, SPIE Bellingham, 1988.
Polarization combining is a well used technique to combine two laser diodes to pump a Nd resonator. However, if more than two laser diodes are required, or if polarization combination is not an effective way to pump the laser rod, another technique must be relied upon.
Thus, a continuing need exists in the state of the art for a technique that enables the combination of a plurality of laser pumping sources to longitudinally pump a solid state laser that is practical and efficient.